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Volts and Amps Pages 142 to 149

Volts and Amps Pages 142 to 149. Instructor Joe Seibert, AL1F. Volts and Amps . Names of electrical units: DC and AC Electrical current is measured in the following units: Amperes The name for the flow of electrons in an electric circuit is: Current

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Volts and Amps Pages 142 to 149

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  1. Volts and AmpsPages 142 to 149 Instructor Joe Seibert, AL1F

  2. Volts and Amps • Names of electrical units: DC and AC • Electrical current is measured in the following units: • Amperes • The name for the flow of electrons in an electric circuit is: • Current • The name for a current that flows only in one direction is: • Direct Current (DC)

  3. Metric Prefixes Metric Exponent English Tera 1012 Trillion Giga 109 Billion Mega 106Million Kilo 103Thousand Centi 10-2 Hundredth Milli 10-3Thousandth Micro 10-6Millionth Nano 10-9 Billionth Pico 10-12 Trillionth

  4. Volts and Amps • Units, kilo, mega, milli, micro • One thousand volts is equal to one kilovolt. • Another way to specify the frequency of a radio signal that is oscillating at 1,500,000 Hertz is 1500 kHz • [or 1.5 megahertz] • 1500 milliamperes is the same as 1.5 amperes. • A hand-held transceiver that has an output power of 500 milliwatts can otherwise be said to output 0.5 watts. • One one-millionth of a volt is equal to one microvolt.

  5. Volts and Amps • Names of electrical units: DC and AC • Electrical Power is measured in the following units: • Watt • The standard unit of frequency is: • Hertz • The basic unit of resistance is: • Ohm • The name for current that reverses direction on a regular basis is: • Alternating Current (AC)

  6. Multimeter(s) Multimeters will measure Voltage, Current and Resistance. Be sure it is set properly to read what is being measured. If it is set to the ohms setting and voltage is measured the meter could be damaged!

  7. Volts and Amps • Conductors and insulators • Copper is a good electrical conductor. • Glass is a good electrical insulator. • The term used to describe opposition to current flow in ordinary conductors such as wires is: Resistance.

  8. Volts and Amps • Two types of electricity: • Direct Current - flows in 1 direction • Battery • 1.5 to 2.5 volts per cell • Car battery nominal 12 volts • Measured strictly by amplitude • Alternating Current - alternates direction • Household • Measured by • Average Amplitude • Frequency (cycles per second)(Hertz)

  9. Alternating & Direct Current V+ DC 0V AC V- time

  10. Volts and Amps • Electrical components • An automobile battery usually supplies about 12 volts [DC]. • An Ammeter is an instrument used to measure the flow of current in an electrical circuit. • A Voltmeter is an instrument used to measure Electromotive Force (EMF) • between two points such as the poles of a battery.

  11. Volts and Amps • Ammeters must be • connected in line • To measure current Ammeter Power Supply Transceiver

  12. Volts and Amps • Volt meters must be connected • across a load to • Measure the voltage Ohmmeter

  13. Volts and Amps • Ohms law relationships • The formula, Voltage (E) equals current (I) multiplied by resistance (R). • E = I*R • The formula, Current (I) equals voltage (E) divided by resistance (R). I = E/R • The formula, Resistance (R) equals voltage (E) divided by current (I). R = E/I

  14. + Meter B Meter A Meter Excercise What circuit quantity would meter A indicate? R Battery voltage What circuit quantity would meter B indicate? The current flowing through the resistor

  15. E R I Ohms Law Electromotive Force, VOLTS The flow of Electrons, AMPERES Resistance to current flow, OHMS

  16. Volts and Amps • Ohms law relationships • If I=3 amperes and E=90 volts. • R = E/I = R = 90/3= 30 • If E=12 volts and I=1.5 amperes. • R = E/I = R = 12/1.5= 8 • If E=120 volts and R=80 ohms. • I = E/R = I = 120/80= 1.5

  17. Volts and Amps • Ohms law relationships • If a current of 0.5 amperes flows through a 2 ohm resistor. • E=I*R E = 0.5 * 2 = 1 volt • If a current of 1 ampere flows through a 10 ohm resistor. • E=I*R E = 1 * 10 = 10 volts • If a current of 2 amperes flows through a 10 ohm resistor. • E=I*R E = 2 * 10 = 20 volts • Current through a 100 ohm resistor across 200 volts. • I=E/R I = 200/100 = 2 amperes • Current through a 24 ohm resistor across 240 volts. • I=E/R I = 240/24 = 10 amperes

  18. Volts and Amps • Ohms law relationships • If a current of 0.5 amperes flows through a 2 ohm resistor. • E=I*R E = 0.5 * 2 = 1 volt • If a current of 1 ampere flows through a 10 ohm resistor. • E=I*R E = 1 * 10 = 10 volts • If a current of 2 amperes flows through a 10 ohm resistor. • E=I*R E = 2 * 10 = 20 volts • Current through a 100 ohm resistor across 200 volts. • I=E/R I = 200/100 = 2 amperes • Current through a 24 ohm resistor across 240 volts. • I=E/R I = 240/24 = 10 amperes

  19. + Meter B R Meter A Substituting I x R for E in the power equation gives: P = I x R x I = R x 2 x I = R x I2 Power Power is measured in Watts P = E x I Ohms law states E= I x R So, for this circuit, the power consumed in the resistor can be calculated by multiplying the value of the resistor times the square of the reading of Meter B.

  20. Volts and Amps • Power calculations • The unit used to describe electrical power is the Watt. • The formula: Power (P) equals voltage (E) multiplied by current (I).P = I * E

  21. Volts and Amps • Power calculations • The unit used to describe electrical power is the Watt. • The formula: Power (P) equals voltage (E) multiplied by current (I).P = I * E

  22. Volts and Amps • Power calculations • You can you determine how many watts are being drawn [consumed] by your transceiver when you are transmitting by measuring the DC voltage at the transceiver and multiplying by the current drawn when you transmit. • How many amperes is flowing in a circuit when the applied voltage is 120 volts DC and the load is 1200 watts. • I = P/E I = 1200/120 = 10 amperes.

  23. Reminder…. • Unit of current… amperes • Electron flow is called current • Current flowing in one direction is DC • Unit of power … Watt • Unit of frequency … Hertz • Unit of resistance … Ohm • Current that reverses direction is AC

  24. Reminder …. • Copper is a good conductor • Glass is a good insulator • Opposition to current flow …. Resistance • Conductors…gold, silver, copper, aluminum • Insulators…air, rubber, plastic, ceramic

  25. Reminder…. • Car battery … 12 volts DC • DC measured by amplitude • AC measured by Average Amplitude • Ammeter measures current • Volt meter measures voltage • Sixty hertz means 60 cycles per second

  26. Reminder… Ohms Law Power calculations

  27. Reminder… • One kilovolt is one thousand volts • 1500 KHz is 1,500,000 Hertz • 1.5 amps is 1500 milliamperes • 500 milliwatts is 0.5 watts • One microvolt is one one-millionth of a volt

  28. Volts and Amps • Test Questions

  29. Electrical current is measured in which of the following units? • Volts • Watts • Ohms • Amperes

  30. Electrical Power is measured in which of the following units? • Volts • Watts • Ohms • Amperes

  31. What is the name for the flow of electrons in an electric circuit? • Voltage • Resistance • Capacitance • Current

  32. What is the name of a current that flows only in one direction? • An alternating current • A direct current • A normal current • A smooth current

  33. What is the standard unit of frequency? • The megacycle • The Hertz • One thousand cycles per second • The electromagnetic force

  34. How much voltage does an automobile battery usually supply? • About 12 volts • About 30 volts • About 120 volts • About 240 volts

  35. What is the basic unit of resistance? • The volt • The watt • The ampere • The ohm

  36. What is the name of a current that reverses direction on a regular basis? • An alternating current • A direct current • A circular current • A vertical current

  37. Which of the following is a good electrical conductor? • Glass • Wood • Copper • Rubber

  38. Which of the following is a good electrical insulator? • Copper • Glass • Aluminum • Mercury

  39. What is the frequency range of the 6 meter band in the United States? • 144 to 148 MHz • 222 to 225 MHz • 420 to 450 MHz • 50 to 54 MHz

  40. T4A11 What is the term used to describe opposition to current flow in ordinary conductors such as wires? • Inductance • Resistance • Counter EMF • Magnetism

  41. T4A12 What instrument is used to measure the flow of current in an electrical circuit? • Frequency meter • SWR meter • Ammeter • Voltmeter

  42. What instrument is used to measure Electromotive Force (EMF) between two points such as the poles of a battery? • Magnetometer • Voltmeter • Ammeter • Ohmmeter

  43. What is the name for the distance a radio wave travels during one complete cycle? • Wave speed • Waveform • Wavelength • Wave spread

  44. What term describes the number of times that an alternating current flows back and forth per second? • Pulse rate • Speed • Wavelength • Frequency

  45. What does 60 hertz (Hz) mean? • 6000 cycles per second • 60 cycles per second • 6000 meters per second • 60 meters per second

  46. Electromagnetic waves that oscillate more than 20,000 times per second as they travel through space are generally referred to as what? • Gravity waves • Sound waves • Radio waves • Gamma radiation

  47. How fast does a radio wave travel through space? • At the speed of light • At the speed of sound • Its speed is inversely proportional to its wavelength • Its speed increases as the frequency increases

  48. How does the wavelength of a radio wave relate to its frequency? • The wavelength gets longer as the frequency increases • The wavelength gets shorter as the frequency increases • There is no relationship between wavelength and frequency • The wavelength depends on the bandwidth of the signal

  49. What is the formula for converting frequency to wavelength in meters? • Wavelength in meters equals frequency in Hertz multiplied by 300 • Wavelength in meters equals frequency in Hertz divided by 300 • Wavelength in meters equals frequency in megahertz divided by 300 • Wavelength in meters equals 300 divided by frequency in megahertz

  50. What are sound waves in the range between 300 and 3000 Hertz called? • Test signals • Ultrasonic waves • Voice frequencies • Radio frequencies

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